KR20100028892A - Internal antenna for tag of real time location system - Google Patents

Abstract

PURPOSE: An antenna device for a tag of a global positioning system is provided to secure reliability of the position estimation by uniformly receiving the signal transmitted from a reader in all directions. CONSTITUTION: A first antenna(11) forms a one-way radiation pattern. A second antenna(12) forms the radiation pattern to the different direction from the first antenna. A switching unit(15) is switched according to an external control signal and forms an isotropic radiation pattern by alternatively connecting the first antenna and the second antenna. The first and second antennas are plated on the different positions on the circuit board with a preset angle. The first antenna is plated on the upper edge of the circuit board.

Description

Antenna device for tag of position tracking system {INTERNAL ANTENNA FOR TAG OF REAL TIME LOCATION SYSTEM}

The present invention relates to a tag of a location tracking system, and more particularly, to an antenna device for a tag of a location tracking system having an isotropic radiation pattern capable of uniformly receiving a signal transmitted from a reader in all directions in a real-time location tracking system.

Real Time Location System (RTLS) refers to the use of certain objects and people in indoors, such as factories and offices, and in a limited range of outdoor, such as yards, parks, and construction sites. It refers to a service that finds a location or provides additional functions based on it.

Currently, Wi-Fi technology is generally used for wireless LAN, but in the future, the development of next-generation technologies such as RTLS reader and UWB application that receive signals transmitted from tags of RTLS and transmit them to servers of RTLS This is going on.

When estimating the position, RTLS, like GPS and LBS, uses triangulation, proximity known as presence, and space into small cells to determine the location of the cell where the object exists. The cell method of estimating is used. Among them, the triangulation method is the most common position estimation method, and the triangulation method is based on RSSI or TDOA technology.

The triangulation method is a very important factor in the accuracy and uniformity of the signal strength (RSSI) reaching the tag from readers in estimating the real-time position of the moving object (RTLS tag) on the two-dimensional plane by the geometric method.

1 shows an external view of a conventional tag for RTLS.

The antenna 5 of the conventionally developed tag 1 is in the form of an external antenna, and the radiation pattern of the antenna 5 is shown in FIG. Referring to FIG. 2, the front and rear surfaces are relatively isotropic, but the radiation patterns on both sides may be tilted or shaded.

This is because the antenna 5 of the tag 1 is not isotropic in estimating the real-time position of the RTLS, and thus the intensity of the signal between all directions received from the reader from the reader is not constant. .

The triangulation method as shown in FIG. 3 is a geometric method. In the RTLS system, the method is most commonly used to estimate a real-time position of an object (tag) moving on a two-dimensional plane. At least three reference points are needed to estimate the real-time position of a moving object on a two-dimensional plane.

In FIG. 3, distances for measuring positions from three reference points are expressed as d1, d2, and d3. The distance from each reference point to the target point for position measurement can be calculated by the Pythagorean theorem of Equation 1 below.

Triangulation Using RSSI In the case of using RSI (Radio Signal Strength Information), a distance between a reference point from a moving object can be obtained through the Friis formula of Equation 2 below.

Where? Is the wavelength of radio waves, c is the speed of radio waves, f is frequency, and L is the transmission loss of the signal transmitted by the mobile entity.

The transmission loss of the transmitted signal is obtained by the difference between the signal transmission strength of the mobile object and the strength of the received signal at the reference point.

In this way, RTLS uses the Wi-Fi technology used in the wireless LAN so that the tags of the RTLS are sent to the RTLS server, or the RTLS reader that receives the signals transmitted from the tags of the RTLS is transmitted to the RTLS server. It is configured to provide the user's location and user information.

In particular, triangulation is a geometrical method in which the accuracy and uniformity of the signal strength (RSSI) reaching the tag from readers are very important factors in estimating the real-time position of a moving object (RTLS tag) on a two-dimensional plane. This, and greatly affects whether or not the radiation pattern of the antenna is isotropic.

An object of the present invention is to provide an antenna device for a tag of a location tracking system having an isotropic radiation pattern capable of uniformly receiving a signal transmitted from the reader in all directions in a real-time location tracking system.

Another object of the present invention is to realize a miniaturization and position estimation by implementing a tag antenna as a built-in plated antenna for miniaturization and low cost, and as a diversity antenna where power is crossed by a switching element for an isotropic radiation pattern. An antenna device for a tag of a location tracking system that can secure reliability at the same time.

Technical means of the present invention for achieving the above object, the first antenna to form a unidirectional radiation pattern; A second antenna forming a radiation pattern in a direction different from that of the first antenna; And switching means for switching in accordance with an external control signal to alternately connect the first and second antennas so that an isotropic radiation pattern is formed through the first and second antennas. .

Specifically, the first and the second antenna is characterized in that the plating is formed at different locations on the circuit board.

The first antenna is characterized in that the plating is formed on the upper edge of the circuit board, the second antenna is formed on the left edge of the circuit board, characterized in that formed in a different direction from the first antenna. .

The first antenna and the second antenna is characterized in that arranged at approximately 90 degrees to each other, the first and second antenna is characterized in that the 'F' or 'L' shape.

The first and second antennas may be any one of a built-in antenna, a monopole antenna, a loop antenna, a dipole antenna, and a chip antenna.

The switching means is characterized in that the switch of the DPDT (Double Port Double Through) type.

As described above, according to the present invention, the tag antenna of the location tracking system is implemented in an isotropic diversity scheme so that signals transmitted from the reader can be uniformly received in all directions, thereby ensuring reliability of position estimation. In addition, since the antenna for the tag is implemented as a built-in antenna, it is possible to miniaturize and reduce the price, which is excellent in terms of portability and economy.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

4 is a diagram illustrating an antenna device for a tag of a location tracking system according to an exemplary embodiment of the present invention, wherein the antenna device 10 includes a first antenna 11, a second antenna 12, a first filter 13, It comprises a second filter 14 and the switching means (15).

The first and second antennas 11 and 12 are configured to interoperate and convert electromagnetic waves in the atmosphere and electrical signals on the conductive lines.

The first and second filters 13 and 14 are configured to remove unwanted frequencies included in the received and transmitted RF signals and to pass only signals of the required frequency band.

The switching means 15 is installed between the first and second antennas 11 and 12 and the first and second filters 13 and 14 to perform a switching operation according to an externally applied control signal so as to transmit an RF signal. It is configured to control.

In addition, R and C filters R and C are formed between the first and second antennas 11 and 12 and the switching means 15 to remove high frequencies and to pass low frequencies.

In addition, the switching means 15 is a switch of a double port double through (DPDT) type, and transmit / receive ports Tx and Rx and first and second antennas according to a plurality of control signals Control_1 and Control_2. 11, 12) switching operation to control and connect the RF signal transmission path according to the requirements of the application characteristics.

Of course, it is also possible to apply the switching means 15 to a single port double through (SPDT) type switch instead of the DPDT type switch. In addition, the switching means 15 may be implemented by applying a pin diode and a micro strip line on a printed circuit board rather than a commercial chip.

Table 1 shows an example in which the switching means 15 is operated according to a plurality of control signals.

Control_1 Control_2 Ant1-Rx Ant1-Tx Ant2-Tx Ant2-Rx One 0 On Off On Off 0 One Off On Off On One One Off Off Off Off 0 0 Off Off Off Off

As shown in Table 1, the DPDT type switching means 15 turns on at least one of the transport channels Tx and Rx when the plurality of input control signals Control_1 and Control_2 are different from each other. When the plurality of control signals Control_1 and Control_2 are identical to each other, all the transmission channels Tx and Rx are turned off. When the first control signal Control_1 is a 'high' signal and the second control signal Control_2 is a 'low' signal, the first antenna 11 and the reception channel Rx are connected to each other, and the second antenna ( 12) and the transmission channel (Tx) is connected on. Meanwhile, when the first control signal Control_1 is a 'low' signal and the second control signal Control_2 is a 'high' signal, the first antenna 11 and the transmission channel Tx are connected to each other. The antenna 12 and the reception channel Rx are connected to each other.

That is, the tag antenna device 10 according to the present invention is implemented in a diversity scheme using a plurality of antennas 11 and 12.

The first and second antennas 11 and 12 have a structure as shown in FIG. 5, unlike the prior art as shown in FIG. 1, the first and second antennas 11 and 12 are printed on a printed circuit board and embedded in a tag. Of course, the embodiment is shown an example in which the first and second antennas are plated on the printed circuit board, but also applicable to monopole antenna, loop antenna, dipole antenna and chip antenna.

In general, when determining the position of an antenna in a circuit board, the position along the length of the ground (the entire board of the circuit board), the distance and position from the instrument, the distance from the noise source, and the distance from the human body when the human body is attached The radiation pattern characteristics of the small internal antenna according to the present invention are greatly influenced according to the present invention.

Therefore, in the present invention, as shown in FIG. 5, not only the design and performance of the first and second antennas 11 and 12 are implemented, but also the isotropic characteristic according to the mounting position in the circuit board.

That is, as shown in FIG. 5, the first antenna 11 is plated to have an approximately 'F' shape at an uppermost edge of the circuit board, and the second antenna 12 is approximately 'F' at a left edge of the circuit board. 'Plated in the form of a ruler.

The first antenna 11 and the second antenna 12 are formed in different directions, and are arranged in an approximately 90 ° direction as shown. Of course, although the first and second antennas 11 and 12 are arranged at 90 ° to each other in the embodiment, it is also possible to arrange them within the range of 0 ° to 180 °.

The maximum length L1 of the first antenna 11 is about 23 mm to 26 mm, and the maximum width W1 is about 5 mm to 6 mm. The maximum length L2 of the second antenna 12 is about 24.5 mm to about 27.5 mm, and the maximum width W2 is about 5 mm to about 6 mm. The maximum length L2 of the second antenna 12 is preferably about 5% to 8% longer than the maximum length L1 of the first antenna 11.

FIG. 6A illustrates radiation pattern characteristics of the first antenna 11 and FIG. 6B illustrates radiation pattern characteristics of the second antenna 12.

As shown in FIG. 6A, the first antenna 11 may be cooked to the right side, and the left side may be tilted or shaded, and the second antenna 12 may be formed as shown in FIG. 6B. In contrast to the first antenna 11, it can be seen that the chef occurs to the left side.

Accordingly, when the first and second antennas 11 and 12 apply power while crossing each other using the switching means 15, when the antenna device 10 of the tag transmits and receives RF to and from a predetermined reader, FIGS. 6A and 6B. The radiation pattern of can be synthesized to implement the isotropic radiation pattern.

That is, the first antenna 11 according to the present invention is plated on the upper end side of the circuit board to form a unidirectional radiation pattern, and the second antenna 12 is located on the left side on the circuit board. Plating is formed in a direction different from) and is configured to form a radiation pattern in a direction different from the first antenna (11). In addition, the switching means 15 is switched according to an external control signal to alternately connect the first antenna 11 and the second antenna 12 so that an isotropic radiation pattern is formed between the first antenna 11 and the second antenna. It is formed through the antenna 12.

In general, a diversity antenna is a method for receiving a wide range of mobile stations in a multi-wave receiving direction by using a receiving antenna having a different directivity, but the first and second antennas 11 and 12 according to the present invention are directed. This is different from the general diversity antenna because it is an isotropic diversity method for implementing isotropy.

In addition, although the first and second antennas 11 and 12 are configured in an approximately 'F' shape to implement an isotropic radiation pattern as shown in FIG. 5, the first and second antennas 11 and 12 may have an approximately 'L' shape as shown in FIG. 7A. It is also possible. Other types include monopole antennas, loop antennas, dipole antennas, and chip antennas.

In addition, as shown in FIG. 7B, four antennas instead of two antennas may be configured, and four antennas may be implemented by applying a cross feed. Of course, when four antennas are configured, a plurality of switching means 15 shown in FIG. 4 may be provided.

The antenna device configured as described above is easy to be mounted on a safety helmet for construction sites as the antenna is embedded in the tag, and is also convenient to use because it can be mounted as a bending type on a human body.

Preferred embodiments of the present invention are disclosed for purposes of illustration, and those skilled in the art will be able to make various modifications, changes, and additions within the spirit of the present invention. Therefore, such modifications, changes and additions should be determined not only by the claims below, but also by equivalents to those claims.

1 is a view showing the outline of a conventional tag for RTLS.

FIG. 2 is a diagram illustrating a radiation pattern by the tag antenna of FIG. 1.

3 is a diagram illustrating a triangulation method for general location tracking and calculation.

4 is a diagram illustrating an antenna device for a tag of a location tracking system according to an exemplary embodiment of the present invention.

5 is a view showing the structure of the antenna of FIG. 4 according to the present invention.

6A and 6B illustrate radiation patterns generated by the first antenna and the second antenna of FIG. 4, respectively.

7A and 7B are diagrams showing the structure of an antenna according to another embodiment of the present invention, respectively.

* Explanation of symbols for the main parts of the drawings

10: antenna device for the tag 11: first antenna

12: second antenna 15: switching means

Claims (8)

A first antenna forming a unidirectional radiation pattern; A second antenna forming a radiation pattern in a direction different from that of the first antenna; And Switching operation according to the external control signal switching means for alternately connecting the first antenna and the second antenna so that the isotropic radiation pattern is formed through the first antenna and the second antenna; Antenna device for. The method according to claim 1, And the first and second antennas are plated at a predetermined angle at different positions on a circuit board. The method according to claim 2, And the first antenna is plated on an upper edge of the circuit board. The method according to claim 2 or 3, The second antenna is formed on the left edge of the circuit board, the antenna device for the tag of the location tracking system, characterized in that formed in a different direction from the first antenna. The method according to claim 2, And the first antenna and the second antenna are disposed at approximately 90 ° to each other. The method according to claim 1, And the first and second antennas are any one of a built-in antenna, a monopole antenna, a loop antenna, a dipole antenna, and a chip antenna. The method according to claim 2, And the first and second antennas have an approximately 'F' or 'L' shape. The method according to claim 1, And said switching means is a switch of a DPDT (Double Port Double Through) type.

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